add a cargoup.sh

[erickt]

It would be nice to have a nightly install script analogous to http://www.rust-lang.org/rustup.sh on the server. This would be especially handy for travis builds so we could standardize on:

# Use something that's not 'ruby' so we don't set up things like
# RVM/bundler/ruby and whatnot. Right now 'rust' isn't a language on
# travis and it treats unknown languages as ruby
language: c

before_install:
  - sudo apt-get update
install:
  - curl -s http://www.rust-lang.org/rustup.sh | sudo sh
  - curl -s http://www.rust-lang.org/cargoup.sh | sudo sh
script:
  - cargo build
  - cargo test

[erickt]

dup of #186.